The present invention relates generally to winding sheet rolls, and, more specifically, to arbors therefor.
Sheet rolls are found in various sizes and forms for various equipment including adding machines, cash registers, Automated Teller Machines (ATMs), and various other forms of printers. Paper in a continuous sheet or ribbon is typically wound around a central tubular core of paper or plastic for example, to provide a paper roll for use in the printer. The wound sheet may be in other forms such as thermal transfer ribbons used in corresponding devices.
The ribbons, or continuous sheets, in the desired form are wound around the core in a corresponding winding machine specifically configured for operation at either low or very high winding speeds. In a typical production method, several cores are mounted coaxially on a common winding arbor or shaft typically in end-to-end contiguous arrangement, and the arbor is rotated for simultaneously winding respective ribbons on each of the adjoining cores. The leading edges of the ribbons may be wound around the cores either in a plain or tuckless configuration, or they may be tucked using a simple 180.degree. fold.
In view of the manufacturing tolerances of the cores and ribbon width, and speed of winding, various problems may develop such as undesirable interleaving of adjoining ribbons, and protrusion of adjoining cores into adjacent wound rolls.
To reduce problems, it is important that the cores be accurately supported on the winding arbor and in the winding machine. A simple arbor in the form of a plain rod must necessarily have a smaller outer diameter than the inner diameter of the cores so that the cores may be readily assembled and disassembled from the arbor. The difference in diameter, however, permits slight misalignment between the adjoining cores and may degrade winding performance.
Another type of arbor known as an air expanding shaft has jaws which may be deployed radially outwardly through the walls of a surrounding tube by pressurizing an internal bladder. However, this type of arbor is made only in relatively large diameters and is not readily scalable downwardly in size to the small diameters required for typical thermal transfer ribbon and paper rolls wound on cores. For example, typical cores may be less than about one inch in inner diameter and down to about 0.375 inches which is extremely small, and renders impractical the downsizing of the large air expanding shaft for this purpose.
An additional problem in small core winding is that the associated arbor is exceptionally slender for mounting a suitable number of cores simultaneously thereon. For example, a winding arbor of about 30 inches in length and an outer diameter less than or equal to one inch is very slender. In order to maximize its bending stiffness, the arbor is typically solid. A hollow arbor would necessarily have an extremely thin wall which would substantially decrease the bending stiffness of the arbor.
Accordingly, it is desired to provide an improved expandable jaw winding arbor using a thin wall tube having an inner diameter less than or equal to one inch while maintaining adequate bending stiffness.